Motor for driving aircraft, located adjacent to undercarriage wheel

ABSTRACT

The invention disclosed is a self-propelled aircraft undercarriage for driving an aircraft on the ground, comprising: an axle; a strut supporting said axle; at least one wheel rotatably mounted on said axle; and drive means for driving said at least one wheel; characterized in that said drive means is disk shaped and is external to said wheel. In one embodiment of the invention, said drive means is mounted on said axle between said strut and said wheel. In a second embodiment, said drive means is mounted on said axle, on the side of said wheel furthest from said strut.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.12/291,257, filed Nov. 6, 2008.

BACKGROUND OF THE INVENTION

The use of separate motors to move aircraft on the ground is helpfulsince it avoids using the aircraft turbines or a separate tug to movethe aircraft.

U.S. Pat. No. 3,711,043 to Cameron-Johnson discloses an aircraft drivewheel having a fluid-pressure-operated motor housed within the wheel andtwo planetary gear stages housed in a gear box outboard of the motor,the final drive being transmitted from a ring gear of the second gearstage, which is inboard of the first stage, to the wheel through anoutput drive quill coupled, through a disc-type clutch if desired, to aflanged final drive member surrounding the inner end of the gear box andbolted to the wheel.

U.S. Pat. No. 3,977,631 to Jenny discloses a wheel drive motorselectively coupled to an aircraft wheel through a rotatably mountedaircraft brake assembly in order to drive the wheels of an aircraft. Thenormally non-rotating stator portion of a conventional aircraft brakeassembly is rotatably mounted about the wheel axle and is rotatablydriven through a planetary gear system by the wheel drive motor.

A solution disclosed in PCT application WO2005/035358 discloses a meshconnected high phase order induction motor, situated in close proximityto, and preferably within, the nosegear. The mesh connection enablesvariable inductance so that the machine has a range of speed/torqueprofiles available.

European Patent No. 0 756 556 B1 to Giovanardi and Centofante disclosesan aircraft having wheel driving means associated with at least one ofthe wheels of the landing gear. A motor powered by the auxiliary powerunit of the aircraft is used to drive the wheels of the landing gear.The assembly comprises an electric or hydraulic motor in operativeconnection with a differential gear assembly, each wheel being mountedon an axle in forward operative connection with a respective half-shaftof the differential gear through a free wheel mechanism.

Motors providing high torque at low speeds are known in the art.Specifically, such motors are known that are designed for the purpose ofpropelling aircraft on the ground.

WO05112584 to Edelson discloses a motor-generator machine comprising aslotless AC induction motor. The motor disclosed therein is an ACinduction machine comprising an external electrical member attached to asupporting frame and an internal electrical member attached to asupporting core; one or both supports are slotless, and the electricalmember attached thereto comprises a number of surface mounted conductorbars separated from one another by suitable insulation. An airgapfeatures between the magnetic portions of core and frame. Electricalmembers perform the usual functions of rotor and stator but are notlimited in position by the present invention to either role. The statorcomprises at least three different electrical phases supplied withelectrical power by an inverter. The rotor has a standard windingconfiguration, and the rotor support permits axial rotation.

WO2006002207 to Edelson discloses a motor-generator machine comprising ahigh phase order AC machine with short pitch winding. Disclosed thereinis a high phase order alternating current rotating machine having aninverter drive that provides more than three phases of drive waveform ofharmonic order H, and characterized in that the windings of the machinehave a pitch of less than 180 rotational degrees. Preferably thewindings are connected together in a mesh, star or delta connection. Thedisclosure is further directed to selection of a winding pitch thatyields a different chording factor for different harmonics. The aim isto select a chording factor that is optimal for the desired harmonics.

Disclosed in WO2006/065988 to Edelson is a motor-generator machinecomprising stator coils wound around the inside and outside of a stator,that is, toroidally wound. The machine may be used with a dual rotorcombination, so that both the inside and outside of the stator may beactive. Even order drive harmonics may be used, if the pitch factor forthe windings permits them. In a preferred embodiment, each of the coilsis driven by a unique, dedicated drive phase. However, if a number ofcoils have the same phase angle as one another, and are positioned onthe stator in different poles, these may alternatively be connectedtogether to be driven by the same drive phase. In a preferredembodiment, the coils are connected to be able to operate with 2 poles,or four poles, under H=1 where H is the harmonic order of the drivewaveform. The coils may be connected together in series, parallel, oranti-parallel.

In U.S. patent application Ser. No. 11/403,402, filed Apr. 12, 2006, amotor-generator machine is disclosed comprising a polyphase electricmotor which is preferably connected to drive systems via meshconnections to provide variable V/Hz ratios. The motor-generator machinedisclosed therein comprises an axle; a hub rotatably mounted on saidaxle; an electrical induction motor comprising a rotor and a stator; andan inverter electrically connected to said stator; wherein one of saidrotor or stator is attached to said hub and the other of said rotor orstator is attached to said axle. Such a machine may be located inside avehicle drive wheel, and allows a drive motor to provide the necessarytorque with reasonable system mass.

International Appl. No. PCT/US2006/12483, filed Apr. 5, 2006, disclosesa motor-generator machine comprising an induction and switchedreluctance motor designed to operate as a reluctance machine at lowspeeds and an inductance machine at high speeds. The motor driveprovides more than three different phases and is capable of synthesizingdifferent harmonics. As an example, the motor may be wound with sevendifferent phases, and the drive may be capable of supplying fundamental,third and fifth harmonic. The stator windings are preferably connectedwith a mesh connection. The system is particularly suitable for a highphase order induction machine drive systems of the type disclosed inU.S. Pat. Nos. 6,657,334 and 6,831,430. The rotor, in combination withthe stator, is designed with a particular structure that reacts to amagnetic field configuration generated by one drive waveform harmonic.The reaction to this harmonic by the rotor structure produces areluctance torque that rotates the rotor. For a different harmonic drivewaveform, a different magnetic field configuration is produced, forwhich the rotor structure defines that substantially negligiblereluctance torque is produced. However, this magnetic fieldconfiguration induces substantial rotor currents in the rotor windings,and the currents produce induction based torque to rotate the rotor.

PCT application no. WO 2007/103266-A2 to Edelson, filed 2 Mar. 2007,discloses a motor comprising: a fixed member comprising a magnetic coreand magnetic windings, having an internal cavity; a driven member insidesaid fixed member, comprising magnetically conductive materials; saiddriven member being situated inside, and able to move within, said fixedmember, wherein magnetic normal force is induced in said fixed memberperiodically, whereby said driven member is periodically moved bymagnetic force with respect to said fixed member, whereby periodicmotion is produced.

BRIEF SUMMARY OF THE INVENTION

The invention disclosed is a self-propelled aircraft undercarriage fordriving an aircraft on the ground, comprising: an axle; a strutsupporting said axle; at least one wheel rotatably mounted on said axle;and drive means for driving said at least one wheel; characterized inthat said drive means is disk shaped and is external to said wheel.

In one embodiment of the invention, said drive means is mounted on saidaxle between said strut and said wheel. In a second embodiment, saiddrive means is mounted on said axle, on the side of said wheel furthestfrom said strut.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The invention will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 is a general view of the first embodiment of the invention.

FIG. 2 is a general view of the second embodiment of the invention.

FIG. 3 is a cross section of a wheel depicting available cavities forthe drive means to occupy.

FIG. 4 is a general view of the third embodiment of the invention.

FIG. 5 a is a cross sectional view of the fourth embodiment of theinvention, viewed from the front of an aircraft.

FIG. 5 b is a cross sectional view of the fourth embodiment of theinvention viewed from above.

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment of the invention, shown in FIG. 1, aself-propelled aircraft undercarriage for driving an aircraft on theground, is disclosed, comprising: an axle 102; a strut 100 supportingsaid axle; two wheels 104 rotatably mounted on said axle; and a drivemeans 106 for driving each said wheel. Said drive means is disk shapedand is external to said wheel. Said drive means is mounted on said axlebetween said strut and said wheel as shown in the figure.

Said strut is a supporting strut as is known in the art of aircraftundercarriages. It may be retractable, telescopically or otherwise, andmay be made of a metal, metal alloy or any other suitable material.

Said axle and said wheel are also as known in the art of aircraftundercarriages and may be of any suitable construction and material.Said wheel may comprise a tire which is as known in the art and may beof any suitable construction and material.

Said drive means is preferably a high phase order electric inductionmotor. Said drive means may also be any other form of electric motorincluding but not limited to an electric synchronous or asynchronous ACinduction motor, permanent magnet brushless DC motor or switchedreluctance motor. In either case, the electric motor can be designed asradial field or as axial field motor. Alternatively, and within thescope of this invention, the motor can also be a hydraulic pump/motorassembly or a pneumatic motor, driven by onboard hydraulic or pneumaticsystems, or may be any drive means capable of driving an aircraft on theground. Preferably, said drive means is one of the motors described inthe background section of this patent. These are able to provide hightorque at low speeds and as such are suitable for aircraft undercarriagewheels.

The length of said drive means is preferably less than its diametersince this is a shape which will provide less wind resistance duringtakeoff and landing. Preferably, said drive means is less than 3 inchesthick and, if on the strut side of the wheel, is substantially diskshaped with a cut-out in the center to allow mounting over the axle,that is, bagel-shaped. ‘Substantially’ in this case means that while themotor may have indents, protrusions, curves, or other non-uniformities,its overall shape is similar to a disk. Said drive means may be a flator a curved disk, or teardrop shape and may be shaped to fit the profileof the side of the wheel, or shaped to fit any component of theundercarriage to which it is adjacent. This will ensure that the minimumof space is occupied by the drive means. Said cut-out may be the sizeand shape of a cross section of the axle, the hub, or any size or maynot be present, that is, the motor may be disk-shaped with no cut-out.An advantage of being less than 3 inches thick is that the drive meanscan fit inside the wheel cavity of most wheels as shown in FIG. 3. Inthe figure, wheel 302 has cavity A 304 which the drive means couldoccupy. Furthermore, since tire 300 bulges outwards beyond the thicknessof the wheel, cavity B 306 is created, which is a further volume, whichthe drive means could also occupy. Thus there is the total cavity A+Bavailable in which to locate the drive means. This is the preferableshape and location since it occupies no extra space in, and will be ableto retract into, the wheel bay during flight with little or noalteration to the bay. This design also provides the maximum surfacearea contact of the wheel with the drive means, which is helpful for theclutch designs described below.

An advantage of the present invention is that, since the drive means isexternal to the wheel as opposed to being an integral part of thestructural design, the drive means is not load bearing, that is, itneither supports the weight of the aircraft during taxi nor bears theimpact of the aircraft landing. The drive means can therefore be thinnerand made of weaker materials, and is therefore cheaper, lighter, andsimpler to construct. Alternatively, this means that a stronger drivemeans can be constructed within the allowed weight limit.

A further advantage of the drive means not being load bearing is thatthere is a reduced certification standard from regulatory authorities inorder to install the drive means on the aircraft.

A yet further advantage is that, since the drive means is not loadbearing, it can be located in any undercarriage wheel. In particular, itcan be located in the main gear or all main gears of an aircraft, whichbear a much greater weight and are therefore not suitable for anin-wheel drive means. Since the main gears bear more weight, they havemuch more traction with the tarmac surface, which enables better controland driving of the aircraft using the drive means. However, theinvention can also be in an aircraft nosewheel.

A yet further advantage is that, since the drive means is not loadbearing, there are fewer problems due to heating of the drive means.

A yet further advantage is that the invention can be installed in anexisting aircraft without the need to replace or modify theundercarriage. The drive means can simply be installed on the axle andconnected to either side of the wheel.

A yet further advantage is that heat can be dissipated through exposureto air more easily than for an in-wheel drive means, as well as byconduction to and through the wheel, thus using the wheel as a heatsink.

In one arrangement the rotor disk is mounted to the wheel (using theexisting or modified bolts) so that the existing wheel bearings alsodouble-function as rotor bearings. That is, since the wheel and rotorare non-rotationally attached, and the wheel has bearings, thesebearings automatically act as bearings for the rotor also. This greatlysimplifies the design of the motor and reduces the weight of the motor.Alternatively, said undercarriage may further comprise a mechanicalcoupling between said wheel and said drive means for connecting saidwheel to said drive means. Said mechanical coupling is preferably ableto be engaged or disengaged, but may also be a permanent coupling.

Said coupling may comprise teeth on said drive means which interlockwith teeth on said wheel to engage said wheel with said drive means.Means may be provided for moving said drive means towards said wheel, toengage said teeth, when the drive means is required to be engaged, andfor moving said drive means away from said wheel when the drive means isrequired to be disengaged. Said means may be hydraulic, or use a linearmotor, for example and without limitation. The component which moves maybe said drive means or said wheel.

Alternatively, said coupling may comprise a magnetorheological fluid(MRF) clutch, which is engaged or disengaged automatically with themotor current.

Alternatively, said coupling may be mounted radially outside the rotorsuch that the centrifugal force from the motor's rotation willautomatically engage the motor to the wheel and move the wheel, whereasthe wheels' rotation without the motor's rotation (during take-off andlanding of the aircraft) will keep the coupling disengaged.

Alternatively, said coupling may comprise a friction pad such as thatfound in clutches or friction brakes, on said drive means, and a furtherfriction pad on said wheel. Means may be provided, which means may behydraulic, for moving said drive means towards and away from said wheel,causing the friction pads to meet to engage the motor and to separate todisengage the motor respectively. The component which moves may be saiddrive means or said wheel. An advantage of this clutch is that noseparate component is required for the clutch, which reduces cost andweight of the invention.

Said clutch may further comprise means for automatically engaging ordisengaging the drive means from the wheel when a predetermined speed isreached, for example, when the speed of the wheel equals the speed ofthe drive means. Preferably, the clutch is anticipated to only engage ordisengage when the speed of the wheel and the drive means are matched,so as to limit wear on the clutch mechanism.

An advantage of the invention having a clutch is that the wheel needonly be engaged after landing. Upon descent and landing, the wheel canbe disengaged from the motor and there is therefore no requirement topre-spin the drive means (and therefore the wheel) up to landing speed.The drive means may remain totally inert in all parts of flight. Thisincreases safety and simplicity.

Said drive means may further comprise means for modifying or adaptingthe speed and/or torque of the motor with respect to the wheel. Thisincludes the use of gears or gear trains, torque converters, planetarygear transmissions, cycloidal reducers and other known speed and torquetransmission means. Said gear, gear train or other transmission meansmay be separate from or integral to the motor. For example and withoutlimitation, motor parts may have gear teeth to make them mesh with othergears.

In a second embodiment of the invention, shown in FIG. 2, theundercarriage has two wheels 204 mounted on axle 202 supported by strut200. Drive means 206 are mounted on said axle, on the side of each saidwheel furthest from said strut, as shown in the figure. An advantage ofthis arrangement over the first embodiment is that heat can bedissipated more easily from this side of the wheel to the surroundingatmosphere. Said drive means may be able to slide on and off said axleand may have a release mechanism for releasing the drive means from theaxle in order to slide off the drive means. This facilitates tirechanging. The release mechanism may be any known in the art. All otherdetails are as in the first embodiment.

In a third embodiment of the invention, shown in FIG. 4, two drive means400 are mounted on the axle 402 for each wheel 404, one drive meansbeing located on each side of the wheel. (Thus for an undercarriagearrangement consisting of two wheels, four drive means would bemounted.) Tire 406 is mounted on wheel 404. The two drive means may beable to move towards and away from the wheel as required for engagingand disengaging, and in their position closest to the wheel may contactand clamp the wheel, acting as caliper brakes. This is preferablyachieved using linear motor activation or may be achieved usinghydraulics. Power may be fed to the drive means closest to the strutdirectly from the strut, and to that furthest from the strut through theaxle. An advantage of this embodiment is that the maximum volume withinthe wheel space is occupied, without taking up extra space outside ofthe wheel. Thus stronger motors, able to provide more torque, can befitted. Furthermore, the surface area of contact of the drive means withthe wheel is maximized to allow more efficient coupling. Furthermore,forces from the drive means are distributed over both sides of thewheel, reducing wheel fatigue and sharing stresses evenly throughout thewheel.

In a fourth embodiment, shown in FIGS. 5 a and 5 b, two drive means 506and 507 are mounted on the axle, one for each wheel 104, one drive meansbeing located on each side of the strut 100. Each drive means has acut-out 508 on its upper part to allow for the vertical part of thestrut 100 to freely move (in vertical direction) to operate the wheel inthe same manner as with no drive means installed. A suitable drivemeans, which allows this cut-out design is preferably an axial fluxelectric motor or a hydraulic or pneumatic motor. All other features areas in the first embodiment.

The invention claimed is:
 1. A self-propelled aircraft undercarriage fordriving an aircraft on the ground, said undercarriage comprising: a. anose or main landing gear strut supporting an axle with one or morewheels, each wheel being rotatably mounted on said axle; b. drive meansfor driving each of said one or more wheels to move an aircraft on theground, wherein said drive means is a motor rotatably mounted over saidaxle completely externally of said one or more wheels in a selectedlocation comprising on a side of said one or more wheels between saidstrut and said one or more wheels or on a side of said one more wheelsfarthest away from said strut, wherein said drive means has asubstantially disk-shaped configuration with a length less than adiameter designed to occupy a minimum amount of space, enabling saiddrive means to be mounted over said axle; and c. coupling meansreleasably connecting said wheel to said drive means when said drivemeans is mounted in said selected location completely external to saidone or more wheels and connected to said one or more wheels on anaircraft without replacing or modifying said undercarriage.
 2. Theself-propelled aircraft undercarriage of claim 1, wherein said drivemeans is mounted completely externally of said one or more wheels in aselected location on a side of said one or more wheels between saidstrut and said one or more wheels, and said drive means has a centralcut out portion corresponding to a cross-section of said axle.
 3. Theself-propelled aircraft undercarriage of claim 1, wherein said drivemeans is mounted in a selected location over said axle on a side of saidone or more wheels farthest away from said strut and further comprises arelease mechanism designed to release said drive means and slide saiddrive means off said axle.
 4. The self-propelled aircraft undercarriageof claim 1, wherein said motor is selected from the list comprisingelectric synchronous AC induction motors, electric asynchronous ACinduction motors, high phase order electric induction motors, permanentmagnet brushless DC motors, switched reluctance electric motors,variable reluctance electric motors, hydraulic pump/motors, andpneumatic motors.
 5. The self-propelled aircraft undercarriage of claim4, wherein said one or more wheels includes drive means engagement meansto automatically engage or disengage said drive means from said one ormore wheels when a predetermined speed is reached, and said couplingmeans comprises a mechanical coupling means adapted to releasablyconnect said drive means to said drive means engagement means on saidone or more wheels.
 6. The self-propelled aircraft undercarriage ofclaim 5, wherein said mechanical coupling means comprises a clutch, agear, or a gear train.
 7. The self-propelled aircraft undercarriage ofclaim 6, wherein said mechanical coupling means is a clutch and saidclutch comprises at least one selected from the list comprising: a.teeth on said wheel drive means engagement means and teeth on said drivemeans, said teeth interlocking to engage said drive means with said oneor more wheels; b. magnetorheological fluid to engage said drive meanswith said one or more wheels; c. said wheel drive means engagement meanscomprising a friction pad and a friction pad on said drive means, saidfriction pads meeting to engage said drive means with said one or morewheels; and d. when said drive means includes a rotor, an elementconnected to the outside of the rotor, wherein said elementautomatically engages with said one or more wheels when said one or morewheels are driven by centrifugal force originating from the rotor'srotational speed and said element disengages from said one or morewheels when the rotor is not turning regardless of rotation of said oneor more wheels.
 8. The self-propelled aircraft undercarriage of claim 7,wherein said drive means includes a rotor, and said clutch comprises anelement connected to the outside of the rotor, wherein said elementautomatically engages with said one or more wheels when said one or morewheels are driven by centrifugal force originating from the rotor'srotational speed, and said element disengages from said one or morewheels when the rotor is not turning, regardless of the rotation of saidone or more wheels.
 9. The self-propelled aircraft undercarriage ofclaim 8, wherein said clutch is designed to automatically engage whenthe drive means is rotating and disengage when only the one or morewheels are rotating.
 10. The self-propelled aircraft undercarriage ofclaim 8, wherein said clutch is designed to engage and then disengagewhen the speed of the drive means and the speed of the one or morewheels are identical, whereby clutch operation is simplified and clutchwear is reduced.
 11. The self-propelled aircraft undercarriage of claim6, wherein said mechanical coupling means is a gear or gear train andsaid gear or gear train is adapted to be integral to said motor.
 12. Theself-propelled aircraft undercarriage of claim 1, wherein said couplingmeans is adapted to automatically connect said drive means to said oneor more wheels when said one or more wheels are mounted, whereby saidone or more wheels can be removed without disassembly of the drivemeans.
 13. The self-propelled undercarriage of claim 4, wherein saidmotor comprises a high phase order electric motor and said motorincludes means for adapting motor speed and torque to values requiredfor moving aircraft on the ground, and said means for adapting motorspeed and torque is at least one selected from the list comprising gearconverters, torque converters, planetary gear transmissions, and cycloidreducers.
 14. The self-propelled aircraft undercarriage of claim 3,wherein said drive means mounted in said selected location comprises aheat sink during operation of said drive means to drive said one or morewheels.
 15. A self-propelled aircraft undercarriage for driving anaircraft on the ground, said undercarriage comprising: a. a nose or mainlanding gear strut supporting an axle with two wheels, each wheel beingrotatably mounted on said axle; b. a pair of drive means, wherein eachdrive means is a motor having a substantially disk-shaped configurationdesigned to occupy a minimum amount of space, with a length less than adiameter and a central cut out portion corresponding to a cross-sectionof said axle enabling said motor to be mounted over said axle and saidmotor is a high phase order electric motor rotatably mounted over saidaxle externally of each wheel to drive each said wheel to move anaircraft on the ground, wherein each said motor is mounted completelyexternally of each said wheel on said axle on a side of said wheelbetween said strut and said wheel; and c. coupling means designed toprovide a selectively engageable and disenagageable connection betweeneach said wheel and each said drive means to drive said wheels when saiddrive means are drivingly mounted on said axle, wherein said drive meansare further configured to be releasably mounted on said axle completelyexternal to said wheels to drive said wheels without replacing ormodifying existing undercarriage structures on an aircraft.